// returns best point
static Pt bwSpiralSearch(BWImage proto, IBWImage img, double instantWinThreshold default 2) {
  float best = -1;
  long bestPt = -1;
  int leewayX = img.getWidth()-proto.getWidth();
  int leewayY = img.getHeight()-proto.getHeight();
  LongIterator it = pixelSpiral_longIterator(leewayX, leewayY);
  while (it.hasNext()) {
    long xy = it.next();
    int x = firstIntFromLong(xy), y = secondIntFromLong(xy);
    float sim = bwImageSectionsSimilarity2(img, proto, x, y, best);
    //print(x + "/" + y + ": " + sim);
    if (sim >= instantWinThreshold)
      ret longToPt(xy);
    if (sim >= best) {
      bestPt = xy;
      best = sim;
    }
  }
  ret longToPtUnlessMinus1(bestPt);
}